I am trying to develop a new app that will have a rating system built in. I would like to ask about usability of existing rating systems, such as the Facebook and Youtube "Like". Are the current rating systems satisfactory or is there a certain point that could be improved? I recognize that all numbers should be readable (i.e. not in graphic form only), but I wonder if there's anything else I should look out for.
Thank you so much for the help.